Nerve conduction velocity tests the speed at which electrical signals pass through a nerve, and electromyography tests muscle health and the health of the nerves that control muscles, according to MedlinePlus. Doctors use nerve conduction velocity to determine whether nerves have been damaged or destroyed.
Physicians employ electromyography in cases where patients experience pain, weakness or abnormal sensations, states MedlinePlus. For people who suffer from muscle weakness, this test can determine whether the cause of the weakness is an injured nerve or a disorder of the nervous system.
Both these tests can cause pain or discomfort in patients. Nerve conduction velocity sometimes feels similar to an electrical shock, but no pain is typically felt after the test is complete, MedlinePlus reports. Electromyography involves the insertion of needles into muscles and the contraction of those muscles. Patients usually sense pain upon the insertion of the needles and experience muscle soreness for a few days following the test.
In preparation for these two tests, MedlinePlus recommends staying warm, because low body temperature slows nerve conduction and can affect test results. Patients undergoing nerve conduction velocity tests need to inform their doctor if they have a pacemaker or cardiac defibrillator, so that a special procedure may be followed. For electromyography, it is best to avoid applying creams and lotions to the skin on the day of the test.